FR2987489A1 - METHOD AND DEVICE FOR MONITORING THE DYNAMIC CONFINEMENT OF AN ENCLOSURE - Google Patents

Abstract

The invention relates to a method and a device for monitoring the confinement of an enclosure (10) comprising walls delimiting an internal volume and an external medium, according to which a differential pressure (AP) is maintained between said internal volume and said medium. outside. According to the invention, the enclosure comprising an orifice (18) in one of its walls establishing a fluid communication between said internal volume and said external medium, said orifice (18) is traversed by a gas flow having a velocity (V ) at least equal to a reference speed V, under the effect of said differential pressure (DeltaP), the method according to which the following steps are carried out: - measuring at predetermined or continuous time intervals the speed (V) of said flow gaseous, and compare this velocity measurement (V) with the reference velocity V, and - when the velocity measurement (V) is lower than the reference velocity V, emit at least one alarm signal.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method and a device for monitoring the dynamic confinement of a containment chamber in overpressure or in an overpressure chamber. depression relative to the external environment. The present invention also relates to an enclosure equipped with such a containment control device. BACKGROUND ART It is known in the nuclear industry to use a containment chamber for the remediation and / or dismantling of radioactive equipment of a nuclear installation, for example due to obsolescence. this equipment or shutting down the installation itself. Figure 1 shows such a containment 1 of the state of the art. This containment 1 comprises a set of vinyl airlock with an airlock in and out of staff 2, an airlock in and out of equipment 3 and an airlock 4. It is in this last airlock 4 that one or more operators perform sanitation and / or dismantling operations for contaminated equipment. The first two airlock 2, 3 each have an access to the outside and direct access to the airlock 4. These two airlock 2, 3 do not communicate with each other so that the first airlock 2 is exclusively reserved for the circulation of the personnel, the second airlock 3 being intended for the only evacuation of the material resulting for example from the disassembly of the radioactive equipment. Each airlock 2-4 is typically formed of a metal structure and flexible vinyl walls. Access to the 2-4 airlock consists of two vinyl sheets 5. These vinyl walls prevent the dispersion of contaminated substances in the environment during remediation work.

Such containment 1 for dismantling and / or sanitation operations is maintained in depression with respect to the reception room receiving this enclosure using a ventilation system either autonomous or connected to the existing network in the reception area.

The ventilation of the locks 2, 3 input / output equipment and personnel is done by air transfer. Only the airlock 4 has a forced air extraction (not shown). During the clean-up and / or dismantling operations, the air flows of the intervention chamber 4 are extracted by a fan preceded by very high efficiency filters (THE filters) capable of trapping particles entrained in the air. thus sucked. This depressurization thus makes it possible to confine and suck the contaminated dust generated for example during the cutting of the radioactive equipment.

The safety of operations relies on the combination of a static containment (tightness of the walls) of the containment and a dynamic containment (ventilation) that keeps the enclosure in depression. The Nuclear Safety Authority (ASN) recommends a depression of such a containment chamber by maintaining a differential pressure of the order of -40 Pa at -80 Pa with the host. This depression value is currently measured at each workstation, but it can not be deduced with certainty the conservation of this value during remediation and / or dismantling of contaminated equipment.

Indeed, this depression value can, for example, suddenly change following a rupture of the static confinement or because of a clogging of the filtration resulting in a decrease in the extraction rate.

The depression value is then no longer in the range of recommended values resulting in fact a cessation of the clean-up and / or dismantling site until the target vacuum value is obtained again. However, such a work stoppage entails significant additional costs and delays, which are incompatible with the economic requirements of the intervening companies. Conversely, there are containment enclosures that require an overpressure to maintain the dust outside of such a chamber. Maintaining overpressure allows to maintain a healthy atmosphere inside the enclosure, that is to say, devoid of damaging dust for operations in this chamber. The safety of the operations is based on the combination of a static containment (tightness of the walls) of the containment and a dynamic containment (ventilation) which keeps the enclosure under overpressure. The present invention aims to overcome these various disadvantages by providing a method and a device for monitoring the confinement of a chamber under vacuum or overpressure relative to the external environment in which the enclosure is placed, simple in their design and their mode operation, guaranteeing the safety of these operations. Another object of the present invention is such a method and such a device for monitoring the dynamic confinement of an enclosure for continuously monitoring the quality of the dynamic confinement of this chamber.

In the remainder of this document, the term "containment" will refer to dynamic containment. The term "enclosure" will refer to a containment enclosure. BRIEF DESCRIPTION OF THE INVENTION For this purpose, the invention relates to a method for monitoring the confinement of an enclosure, said enclosure comprising walls defining an interior volume and a medium external to said enclosure, according to which there is maintained continuously a differential pressure (OP) between the interior volume of the enclosure and said external environment. According to the invention, the enclosure comprising an orifice in one of its walls establishing a fluid communication between said internal volume and said external medium, said orifice is traversed by a gas flow having a speed (V) at least equal to one reference speed Vref, under the effect of said differential pressure (OP), process according to which the following steps are carried out: - measuring at predetermined time intervals or continuously the speed (V) of said gaseous flow, and comparing this measurement velocity (V) with reference speed Vreference, - when velocity measurement (V) is lower than reference velocity Vreference, emit at least one alarm signal.

This monitoring method therefore comprises a step of monitoring in time the speed of the gas flow entering the chamber when it is in depression relative to the external environment, or leaving the chamber when the latter is in overpressure. relative to the external environment, by continuously measuring or at predetermined time intervals, for example periodic intervals, the speed of this gas flow. Advantageously, this speed measurement is performed at the right of the orifice of predetermined size. The speed of the gas stream entering or leaving the containment chamber through the orifice is directly related to the extraction flow rate, respectively to the intake flow rate, (Q) of the ventilation system of this chamber. For example, the gas flow entering or leaving the containment chamber is air or a neutral gas. The process of monitoring the confinement of a vacuum enclosure with respect to the external environment ensures, through the measurement of a simple parameter throughout the sanitation and / or dismantling operations, to guarantee the quality of the confinement and thereby avoid any risk of contamination outside the enclosure. The method for monitoring the confinement of an enclosure in overpressure with respect to the external environment ensures, through the measurement of a simple parameter throughout the operations carried out in the enclosure, to guarantee the quality of the confinement and thus avoid any risk of contamination. towards the inside of the enclosure. This speed criterion is simple to: - Remember, - Get, - Measure, - Follow in time. This reference speed: - Guarantee the proper functioning of the containment system. - Removes the constraints related to the depression of the enclosure thus reducing the operating costs of the sites, - or eliminates the constraints related to the setting overpressure of the enclosure.

In various particular embodiments of this confinement monitoring method, each having its particular advantages and capable of numerous possible technical combinations: said differential pressure (OP) between the interior volume of the enclosure and said external medium is established by means of less a ventilation system of said enclosure. Having determined a reference ventilation flow rate (Qref) of said enclosure by said at least one ventilation system, the following steps are performed: - measuring the ventilation rate (Q) of said enclosure, - comparing the ventilation flow measurement (Q) thus obtained with the reference flow rate (Qref) to determine whether the ventilation flow rate has dropped, and - possibly adjust the ventilation flow rate (Q) to generate a flow of gas passing through said orifice with a speed at least equal to said reference speed Vreference- "Ventilation flow" is understood to mean a flow rate for extracting or admitting a gaseous flow such as air as a function of the operating mode for extracting or admitting the at least one system ventilation. The ventilation rate (Q) of said chamber is advantageously measured periodically. For purely illustrative purposes, the ventilation rate is measured at a frequency of one measurement per day, and even more preferably one measurement per hour.

For example, the ventilation rate may have decreased following the clogging of one or more filtration stages of the enclosure. The reference ventilation flow rate (Qref) is advantageously recorded on a storage unit. Alternatively, the ventilation flow rate (Q) of said chamber being equal to or substantially equal to the reference flow rate (Qref), the leakage or leaks of said chamber are localized and the leak or leaks is sealed. As a purely illustrative example, this location of the leak or leaks resulting in a loss of static confinement of the chamber, can be achieved by scanning a tracer gas in the chamber and the detection by means of one or more distributed analyzers. outside the tracer gas enclosure and its concentration. Preferably, the gas thus swept into the chamber is a neutral gas. Said at least one ventilation system is chosen from the group comprising: a system for extracting a gas stream, a system for admitting a gas stream , a reversible system capable of switching between a gas flow extraction mode and a gas flow admission mode and combinations of these elements. said differential pressure (OP) between the interior volume of the chamber and said external medium is established by at least one gas flow supply source having an intake flow (Q). For purely illustrative purposes, this at least one gas flow supply source comprises at least one pressure vessel of a gas flow. This or these pressure vessels can be connected to a gas flow supply circuit in the enclosure. Of course, depending on the needs, it is possible to introduce one or more different gas streams. Having determined a reference intake flow (Qref) of said enclosure by said at least one gas flow supply source, the following steps are performed: - measuring the intake flow (Q) of said enclosure, - compare the intake flow rate measurement (Q) thus obtained with the reference flow rate (Qref) to determine whether the intake flow (Q) has decreased, and - possibly adjust the intake flow (Q) to generate a flow gaseous passing through said orifice with a speed at least equal to said reference speed Vreference Alternately, the intake flow rate (Q) in said chamber being equal to or substantially equal to the reference flow rate (Qref), locating the leakage or leaks of said pregnant and one plugs said leaks. said reference speed Vreference is at least equal to 1 m.s-1. The invention also relates to a device for implementing the containment monitoring method as described above. According to the invention, this device comprises: a duct of diameter D intended to be mounted on an orifice of a wall of said enclosure, said duct comprising a non-return valve which closes said duct to prevent the passage of a flow gaseous from the inside of the enclosure towards the external environment when said enclosure is at a vacuum with respect to the external environment, or from the external environment towards the interior volume of said enclosure when said enclosure is at overpressure with respect to the external environment, and a means for measuring the speed of the gas flow moving in said duct. For example, this speed measuring means is a hot wire anemometer or a propeller anemometer. Since the anemometer is a hot-wire anemometer, this anemometer is advantageously placed at a distance of at least five (5) x D from the ends of said duct so as to guarantee the most reliable measurement possible. Preferably, the device further comprises an audible and / or luminous alarm for transmitting at least one alarm signal when the speed (V) measured by the speed measuring means is less than a speed threshold value such as the speed reference Vreference.

Advantageously, the speed measuring means being connected to a processing unit of the signal emitted by this measuring means, this or these alarms can be connected to the processing unit and be controlled by the latter. Alternatively, the processing unit itself emits the alarm. The invention also relates to an enclosure comprising at least one interior volume defined by walls and at least one device for depression or overpressure of the interior of said chamber relative to the external environment in which it is placed. According to the invention, this enclosure comprises a device for implementing the containment monitoring method as described above, this device being mounted on an orifice of one of said walls of the enclosure delimiting said interior volume. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages, aims and particular features of the present invention will emerge from the description which follows, for an explanatory and in no way limiting purpose, with reference to the appended drawings, in which: FIG. FIG. 2 shows a vacuum enclosure according to a particular embodiment of the present invention, this enclosure comprising a device for controlling the leaktightness. 3 schematically represents the device for checking the tightness of the chamber of FIG. 2 DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Firstly, it should be noted that the figures are not to scale. Figure 2 shows an enclosure 10 which is in depression relative to the external environment according to a preferred embodiment of the present invention. This enclosure 10 comprises a metal structure covered with vinyl sheets delimiting a first airlock 11 for the circulation of the operator or operators and a second airlock 12 intended to receive and allow the evacuation of the structural work resulting from the cleaning and / or dismantling of contaminated element, equipment or facility. The first and second chamber 11, 12 are distinct from one another and do not communicate with each other. By way of example only, the volume of the first airlock 11 is 5 m3 while the volume of the second airlock 12 is 15 m3.

These vinyl walls also delimit a third chamber 13, called intervention chamber and having a larger volume than the other two, for example 40 m3.

Of course, an enclosure 10 may have varied volumes depending on the dimensions of the elements, equipment or contaminated facilities to be treated. It is in this intervention chamber 13 that the sanitation and / or dismantling operations themselves are carried out.

This third chamber 13 comprises an air extraction installation ensuring the depression of the chamber relative to the external environment in which the chamber is placed. This external environment is here the hall of a building housing the enclosure 10. Advantageously, this air extraction system sucking air into the third volume 13 comprises an extraction device 14 such as a fan, whose extraction rate is adjustable. The installation also comprises an evacuation circuit 15 to which the air extraction device 14 is connected, this circuit comprising an installation for filtering the sucked air. Advantageously, this evacuation circuit 15 also comprises a flowmeter 16 for precisely measuring the flow rate Q of the extraction device. By way of example, this flowmeter 16 comprises an anemometer connected to a calculation unit for calculating the extraction flow rate from the extraction speed measured by the anemometer. Alternatively, a pitot probe would also be suitable for measuring the extraction rate.

One of the walls 17 of this third volume has an opening receiving a conduit 18. A first end 19 of this conduit opens into the third chamber 13 of the chamber while its other end 20 opens out of this chamber . This duct 18 thus establishes a fluid communication between the environment outside the enclosure and the interior volume of this enclosure. As the enclosure is at a vacuum with respect to the external environment, an incoming air flow is generated in this duct 18. This duct 18, which in the embodiment in question has a diameter of 100 mm, is preferably made of a material rigid plastic such as polyvinyl chloride (PVC), being assembled sealingly with the vinyl wall 17 of the third lock. Advantageously, the duct 18 is light so as not to weaken the vinyl wall 17 on which it is mounted. Preferably, the attachment of this conduit 18 to the wall of the enclosure, is achieved by means of fastening lugs 21, the sealing of the assembly being here made by bonding for example using an adhesive tape. The end 19 of the duct leading into the enclosure preferably comprises a check valve 22 allowing the passage of air from the outside to the interior of the chamber 10 but blocking the flow of the air in the other direction to prevent any risk of contamination outside the enclosure. In this conduit 18 is placed a propeller anemometer 23 for continuously measuring the speed of the incoming air flow. Advantageously, the axis of rotation of the helix is kept parallel to, or substantially parallel to, the flow axis of the incoming air flow circulating in the duct 18. The assembly is connected to a unit 24 for processing the air. signal emitted by the anemometer 23 such as an electronic box, by a connecting element 25 such as a cable.

The electronic box allows the reading of the measured speed and supports the visual and / or audible alarm 26 sounding when the measured speed is lower than a reference speed Vreference taken here equal to 1 ms-1 by way of example. Thus, in order to obtain the confinement enclosure 10 as described above for a dismantling and / or remediation worksite, the following steps will have been performed: - make a calibrated diameter orifice equal to 100 mm, also as a for example, on a wall of this chamber, - adjust the extraction rate of the chamber so as to obtain a speed at least equal to 1 ms-1 measured at the orifice of the calibrated orifice using the anemometer propeller, this speed of 1 ms-1 being called reference, - measure the rate of extraction of the enclosure for this speed and the pressure drop of the filtration with the pressure drop of the clogging compensation register (point of set of filtration).

In a more general manner, it will be determined in advance according to the dimensions of the orifice and the vacuum chamber, the value Vreference of the reference speed of the incoming or outgoing gas flow used to trigger the alarm. For this and in a particular embodiment of the invention, a tracer gas is introduced into the chamber. This tracer gas is preferably an inert gas such as sulfur hexafluoride (SF6) or helium (He). The main advantage of these tracer gases is their very high chemical inertia even at high temperature and their properties to be detectable continuously and in real time, by mass spectrometry for helium and by infrared analysis for SF6. This tracer gas is swept into the chamber, for example by means of an attached blower and placed in the center of the third lock chamber 13. The concentration of this tracer gas is detected and measured outside the chamber 10 at the using one or more analyzer apparatus for different velocity values of the gas flow such as air, entering or exiting through the fixed diameter orifice and under different operating conditions of that enclosure. The data thus obtained are compared and the smallest of these speed values is retained for which the concentration of the tracer gas detected outside the enclosure 10 under the various operating conditions envisaged is less than or equal to a threshold value. This threshold value corresponds here to a negligible transfer to the outside of the tracer gas. As a purely illustrative example, the different service conditions can be simulated by input / output scenarios of the intervention airlock such as those described below: - Scenario 1: entry of an operator in the airlock / exit of the personnel 11 then in the intervention chamber 13. Exit of the interception chamber 13 by the personnel entry / exit airlock 11, wait time of one minute to simulate the undressing time of the operator , then output to the outside of the enclosure 10; - Scenario 2: like scenario 1 but in "degraded" version. The operator does not wait a minute in the personal airlock and goes directly outside; Scenario 3: hardware entry simulation in the material lock 12 without equipment, exit of the operator, entry of the operator in the entry / exit airlock of the personnel 11 and then in the intervention airlock 13.

Simulation of material recovery in the material lock 12, exit of the airlock by the personnel entry / exit airlock 11, waiting time of one minute to simulate the undressing time of the operator, then exit out of the enclosure 10; - Scenario 4: entry / exit of material in "degraded" version without passing through the entry / exit airlock of the personnel 11, nor mark a waiting time of one minute; Scenario 3: as scenario 3 but with a device for transporting material such as a practice wheel; - Scenario 4 ': like scenario 4 but with a roll-practice; - Scenario 5: as scenario 1 but by the material airlock; - Scenario 6: No simulation of operator passages but vinyl doors between the entry / exit airlock of staff 11 and equipment 12 and the open exterior, then, in a second step, opening of the vinyl door between the airlock 13 and the airlock 12. It should be noted that Scenarios 1 and 3 are the scenarios usually applied in controlled area. The interest to realize the scenarios 2, 4, 5 and 6 is to test other cases a priori more penalizing likely to occur in use.

Claims (15)

REVENDICATIONS1. A method of monitoring the confinement of an enclosure, said enclosure (10) having walls delimiting an interior volume and a medium external to said enclosure, according to which a differential pressure (OP) is continuously maintained between the internal volume of the enclosure enclosure and said external medium, characterized in that - the enclosure having an orifice (18) in one of its walls establishing a fluid communication between said internal volume and said external medium, said orifice (18) is traversed by a gas flow having a speed (V) at least equal to a reference speed Vref under the effect of said differential pressure (OP), in which method the following steps are carried out: - measuring at predetermined time intervals or continuously the speed (V) of said gaseous flow, and comparing this speed measurement (V) with the reference speed Vreference, - when the speed measurement (V) is less than the vi reference speed Vreference, emit at least one alarm signal. 2. Method according to claim 1, characterized in that said differential pressure (OP) between the interior volume of the chamber and said external medium is established by at least one ventilation system. 3. Method according to claim 2, characterized in that having determined a reference ventilation rate (Qref) of said enclosure (10) by said at least one ventilation system, the following steps are carried out: measuring the flow rate of ventilation (Q) of said enclosure (10), - comparing the ventilation flow rate measurement (Q) thus obtained with the reference flow rate (Qref) to determine whether the ventilation flow rate has decreased, and - possibly adjusting the ventilation flow rate (Q) for generating a gas flow passing through said orifice with a velocity at least equal to said reference velocity Vreference. 4. Method according to claim 2 or 3, characterized in that the ventilation rate (Q) of said enclosure (10) being equal to or substantially equal to the reference flow (Qref), locating the leaks or said enclosure ( 10) and the one or more leaks are sealed. 5. Method according to any one of claims 2 to 4, characterized in that said at least one ventilation system is selected from the group consisting of: a system for extracting a gas stream, an intake system of a gas flow, a reversible system capable of switching between a gas flow extraction mode and a gas flow admission mode, and combinations of these elements. 6. Method according to claim 1, characterized in that said differential pressure (OP) between the interior volume of the chamber and said external medium is established by at least one gas flow supply source having an intake flow rate ( Q). 7. Method according to any one of claims 1 to 6, characterized in that it performs beforehand, the following steps for determining said value Vreference of the reference speed of the gas stream: - introducing a tracer gas in said chamber ( 10), - detecting and measuring the concentration of said tracer gas outside said enclosure (10) by means of one or more analyzer apparatus for different velocity values of the gas stream entering through said orifice (18) of fixed diameter and under different operating conditions of said enclosure, - compare the data thus obtained and retain the smallest of said speed values for which the concentration of said tracer gas detected outside said enclosure (10) under the various conditions of considered, is less than or equal to a threshold value. 8. Method according to any one of claims 1 to 7, characterized in that said incoming gas stream is air or a neutral gas. 9. Method according to any one of claims 1 to 8, characterized in that said reference speed Vreference is at least equal to 1 m.s-1. 10. The method of claim 9, characterized in that said reference speed Vreference is strictly equal to 1 m.s-1. 11. Device for implementing the process for monitoring the confinement of an enclosure according to any one of claims 1 to 10, characterized in that it comprises at least: a duct of diameter D (18) for being mounted on an orifice of a wall of said enclosure (10), said duct comprising a non-return valve (22) which closes said duct (18) to prevent the passage of a gas flow from inside the enclosure (10) towards the outside environment when said enclosure is at a vacuum with respect to the external environment, or from the outside environment towards the interior volume of said enclosure when said enclosure is at overpressure with respect to the external environment, and - means (23) ) for measuring the velocity of the gas flow moving in said duct. 12. Device according to claim 11, characterized in that said means (23) for measuring speed is an anemometer. 13. Device according to claim 11 or 12, characterized in that it further comprises an audible and / or luminous alarm (26) for emitting at least one alarm signal when the speed (V) measured by the means (23) ) velocity measurement is less than a speed threshold value. 15 14. Containment chamber comprising at least one interior volume delimited by walls and at least one device for depressurization, or in excess pressure, of this interior volume of said chamber relative to the external environment in which said chamber is placed, characterized in that it comprises a device for implementing the monitoring method 20 according to any one of claims 11 to 13, this device being mounted on an orifice of one of said walls of the enclosure defining said interior volume. 15. Enclosure according to claim 14, characterized in that it comprises a flowmeter for measuring the extraction flow of said vacuum device, or the intake flow of said overpressure device, said flowmeter comprising an anemometer or a pitot probe for measuring the extraction or admission speed, said anemometer or pitot probe being connected to a calculation unit for calculating the extraction or admission flow, respectively, from the speed Extraction, respectively admission, thus measured.